title: Determination of free chlorine concentrations needed to prevent Escherichia coli O157:H7 cross-contamination during fresh-cut produce wash.
abstract: This study was conducted to investigate the effect of free chlorine concentrations in wash water on Escherichia coli O157:H7 reduction, survival, and transference during washing of fresh-cut lettuce. The effectiveness of rewashing for inactivation of E. coli O157:H7 on newly cross-contaminated produce previously washed with solutions containing an insufficient amount of chlorine also was assessed. Results indicate that solutions containing a minimum of 0.5 mg/liter free chlorine were effective for inactivating E. coli O157:H7 in suspension to below the detection level. However, the presence of 1 mg/liter free chlorine in the wash solution before washing was insufficient to prevent E. coli O157:H7 survival and transfer during washing because the introduction of cut lettuce to the wash system quickly depleted the free chlorine. Although no E. coli O157:H7 was detected in the wash solution containing 5 mg/liter free chlorine before washing a mix of inoculated and uninoculated lettuce, low numbers of E. coli O157:H7 cells were detected on uninoculated lettuce in four of the seven experimental trials. When the prewash free chlorine concentration was increased to 10 mg/liter or greater, no E. coli O157:H7 transfer was detected. Furthermore, although rewashing newly cross-contaminated lettuce in 50 mg/liter free chlorine for 30 s significantly reduced (P = 0.002) the E. coli O157:H7 populations, it failed to eliminate E. coli O157:H7 on lettuce. This finding suggests that rewashing is not an effective way to correct for process failure, and maintaining a sufficient free chlorine concentration in the wash solution is critical for preventing pathogen cross-contamination.
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Environmental Microbial and Food Safety Laboratory, Beltsville, MD 20705, USA. yaguang.luo@ars.usda.gov
authors.forename: Yaguang
authors.initials: Y
authors.lastname: Luo
authors.forename: Xiangwu
authors.initials: X
authors.lastname: Nou
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
authors.forename: Isabel
authors.initials: I
authors.lastname: Alegre
authors.forename: Ellen
authors.initials: E
authors.lastname: Turner
authors.forename: Hao
authors.initials: H
authors.lastname: Feng
authors.forename: Maribel
authors.initials: M
authors.lastname: Abadias
authors.forename: William
authors.initials: W
authors.lastname: Conway
mesh_terms: D002713:Chlorine / Q000494:pharmacology*; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004202:Disinfectants / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000254:growth & development; D005506:Food Contamination / Q000032:analysis / Q000517:prevention & control*; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D006801:Humans; D018545:Lactuca / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D014675:Vegetables / Q000382:microbiology
chemical_list: D004202:Disinfectants; D002713:Chlorine